Novel compositions of matter for use in the treatment of aqueous systems

ABSTRACT

A method of inhibiting scale formation by salts of calcium, magnesium, barium and strontium from aqueous solutions, by adding to the aqueous solution a minor proportion of a product comprising a telomer of formula I: ##STR1## or a salt thereof, wherein X is CO 2  H when Y is H and vice versa, B and B&#39; are each hydrogen or B is CH 3  when B&#39; is H or vice versa, m is an integer from 2 to 100 and n is 0 or 1, R is an hydroxyl group, alkyl having from 1-22 carbon atoms substituted by one or more carboxyl groups.

The present invention relates to new compositions of matter and to theiruse in the treatment of aqueous systems.

The majority of natural waters, and aqueous systems in general, containdissolved salts of metals such as calcium, magnesium, barium andstrontium. When the water or aqueous system is subjected to heating, thedissolved salts may be converted to insoluble salts and deposited asscale on heat transfer surfaces in contact with the water or aqueoussystem. If the water or aqueous system is concentrated even withoutheating, insoluble salts may also be precipitated.

Salt precipitation and scale deposition are troublesome and can causeincreased costs in maintaining aqueous systems in good working order.Among the problems caused by scale deposits are obstruction of fluidflow, impedance of heat transfer, wear of metal parts, shortening ofequipment life, localised corrosion attack, poor corrosion inhibitorperformance, and unscheduled equipment shutdown. These problems canarise in water or oil wells, water pipes, steam power plants, waterdesalination plants, reverse osmosis equipment utilising aqueoussolutions, heat exchange equipment, and equipment concerned with thetransport of products and by-products in aqueous media (e.g. fly ashformed during the combustion of coal in the production of electricity).The range of temperature at which these processes operate is wide, forexample ambient temperatures are used for cooling water and elevatedtemperatures are used for steam power plants.

One method used to overcome the disadvantage associated with scaleformation has involved the dismantling of equipment to enable theaccumulated deposits to be cleaned out. This procedure is costly anddoes not prevent scale redeposition. Another method, described by M.N.Elliot, Desalination, 6, (1969), p.87 involves the use of strong alkalisolution for the removal of, in particular, sulphate scale. It has beenalleged that under suitable conditions of temperature and time thealkali treatment eventually provides an initial break up of the scale,which can then be removed by mechanical means. Such a method requiresconsiderable time, and the removal of scale subsequent to treatment isoften difficult.

There is, therefore, a need in this field for a composition which can beadded to water or aqueous systems in very small quantities and which canreduce the rate at which insoluble salts are precipitated over a widetemperature range. Furthermore when any scale is formed, it shoulddesirably be easily removable from surfaces by mechanical means, asdiscussed in the article by D.R. Sexsmith, Industrial Water Engineering,Dec. 1969, p.20.

A wide range of additives has been suggested for addition to water oraqueous systems for these purposes, among them polyphosphates, ligninsulphonic acids, polycarboxylic acids such as polyacrylic acid andpolymaleic acid. The polyphosphates ultimately allow the formation of asoft friable scale which is easily removed from the surfaces, whereaspolyacrylic acids eventually allow the formation of a uniform, hard,adherent, egg-shell like scale. However, polyphosphates are lesseffective above 90° C since they hydrolyse to orthophosphates. Thisprecludes their use in high temperature desalination systems asdisclosed by M.N. Elliott, Desalination, 6 (1967), p.90. Polymaleic acidof molecular weight <2,000 ultimately allows, at these highertemperatures, the formation of a non-uniform scale which is relativelyeasily removed, as described in U.S. Patent No. 3,919,258.

The present invention relates to telomeric compounds which show goodcontrol of calcium carbonate, calcium sulphate and magnesium hydroxidescales and more importantly modify the crystal structure of the scale sothat it is non-uniform and easily removable.

According to the present invention, therefore, there is provided amethod of inhibiting scale formation by salts of calcium, magnesium,barium and strontium from aqueous solutions over a wide range by addingto the aqueous solution a minor proportion of a product comprising atelomer of formula I: ##STR2## or a salt thereof, wherein X is CO₂ Hwhen Y is H and vice versa, B and B' are each hydrogen or B is CH₃ whenB' is H or vice versa, m is an integer of from 2 to 100 and n is 0 or 1,R is a. hydroxyl group, an aliphatic residue having from 1 to 22,preferably 13 to 20 carbon atoms, an alicyclic residue having from 5 to12 carbon atoms or an aromatic residue having from 6 to 20 carbon atoms,each unsubstituted or optionally substituted by one or more mercapto,hydroxyl, alkoxy, carbonyl, carboxyl, or alkoxycarbonyl or alkoxysulphonyl groups in which the alkoxy groups contain up to 20 carbonatoms or a residue having the following formula: ##STR3## in which B,B', X and Y have their previous significance and p is an integer from 2to 100 and may be the same as m or different, or a group having one ofthe following formulae: ##STR4## wherein X, Y, B, B', n and p have theirprevious significance, or a mixture of telomers of formula I.Preferably, n is 0 and m is preferably 2 to 20 and especially 5 to 20.

The grouping ##STR5## may be a sulphoxide (when n = 0) or thecorresponding sulphone (when n = 1).

When R is an aliphatic residue, it is preferably an alkyl residue havingfrom 1 to 22, especially 13 to 20 carbon atoms. Examples of alkylresidues R are methyl, ethyl, n-propyl, isopropyl n-butyl, t-butyl,n-hexyl, n-octyl, n-decyl, n-tridecyl, n-tetradecyl, n-hexadecyl,n-octadecyl, n-eicosyl and n-docosyl residues.

When R is an alicyclic residue, it is preferably a cycloalkyl residuehaving from 5 to 12 carbon atoms, especially a cyclopentyl or cyclohexylresidue.

Preferred aromatic residues R are phenyl and naphthyl residues.

Preferred examples of substituted residues R include cyclohexyl, phenyland especially alkyl residues substituted by one or more mercapto,hydroxyl, alkoxy, carbonyl, carboxyl, alkoxycarbonyl or alkoxy -sulphonyl groups. Particularly preferred substituted residues R arealkyl residues having from 1 to 6 carbon atoms substituted with one tothree hydroxy or carboxyl groups e.g. carboxymethyl, carboxyethyl,1,2-dicarboxyethyl, carboxypropyl, carboxybutyl,2-hydroxyethyl,2,3-dihydroxypropyl, and 1 mercapto-1,2-dicarboxy ethylresidues, or a group having the formula:- ##STR6## wherein X, Y, B, B',m and p have their previous significance.

The amount of the compound of formula I which may be used in the methodaccording to the present invention is preferably within the range offrom 0.2 part to 500 parts per million, especially from 0.2 part to 10parts per million, based on the water to be treated.

The compounds of formula I and mixtures thereof including reactionproducts containing compound of formula I and salts thereof areparticularly effective in inhibiting the deposition of calcium sulphate,magnesium hydroxide and calcium carbonate scales.

Mixtures of telomers of formula I are effective scale inhibitors whenused in the method of the present invention and such mixtures may beobtained by admixing telomers of formula I having differing values for mand/or n and/or p.

Examples of the bases with which compounds of formula I may be reactedin order to form partial or complete salts are the hydroxides andcarbonates of sodium, potassium and ammonia. Similarly, organic basesmay be employed. For instance, primary, secondary and tertiary alkyl andsubstituted alkyl amines may be employed in which the total carbonnumber does not exceed twelve, such as triethanolamine. These salts alsohave good activity in inhibiting the precipitation of insoluble saltsfrom aqueous solution.

The compounds of formula I, reaction products containing compounds offormula I and salts thereof are effective in inhibiting the depositionof scale and precipitation of salts from aqueous solutions. The scaleforming salts are derived from calcium, magnesium, barium or strontiumcations and anions such as sulphate, carbonate, bicarbonate, hydroxide,phosphate or silicate.

The majority of the compounds of formula I are new and form part of thepresent invention. However, the compounds of formula I wherein R is analkyl residue having from 6 to 12 carbon atoms are described in U.S.Pat. Nos. 3,699,069 and 3,759,860. The U.S. Patent Specifications donot, however, suggest that the said compounds could be used in aqueoussystems, rather that they are useful in textile coating applications.

Accordingly, the present invention also provides a compound having theformula:- ##STR7## wherein X, Y, B, B', m and n have their previoussignificance and R₁ is an hydroxyl group, an unsubstituted aliphaticresidue having from 13 to 22 carbon atoms, an unsubstituted alicyclicresidue having from 5 to 12 carbon atoms or an unsubstituted aromaticresidue having from 6 to 20 carbon atoms, or an aliphatic residue havingfrom 1 to 22 carbon atoms, an alicyclic residue having from 5 to 12carbon atoms or an aryl residue having from 6 to 20 carbon atoms, eachsubstituted by one or more mercapto, hydroxyl, alkoxy, carbonyl,carboxyl, alkoxycarbonyl or alkoxysulphonyl groups in which the alkoxygroups contain up to 20 carbon atoms, or a residue having one of theformula II, III, IV or V as hereinbefore defined.

Preferred instances of m and n are the same as those indicated forcompounds of formula I.

Similarly, preferred examples of substituent R₁ are the same as thepreferred examples of substituent R in the compounds of formula I.

Examples of new compounds of formula IA are those having the followingresidues R₁, B and B' and the following values of m and n:-

    ______________________________________                                        R.sub.1     B        B'        m      n                                       ______________________________________                                        CH.sub.2 CO.sub.2 H                                                                       H        H          9     0                                       CH.sub.2 CO.sub.2 H                                                                       H        H          9     1                                       HOCH.sub.2 CH.sub.2                                                                       H        H          8     0                                       HOCH.sub.2 CH.sub.2                                                                       H        H          8     1                                       CH.sub.2 CO.sub.2 H                                                                       H        CH.sub.3  11     0                                       (CH.sub.2).sub.2 CO.sub.2 H                                                               H        CH.sub.3  11     1                                        ##STR8##   H        H         13     0                                        ##STR9##   H        H         15     0                                       C.sub.22 H.sub.45                                                                         H        H         16     0                                        ##STR10##  H        CH.sub.3  12     0                                        ##STR11##  H        CH.sub.3  12     1                                        ##STR12##  H        H         12     0                                       OH          H        H         13     1                                        ##STR13##  H        H         12     0                                       Compounds of                                                                  Formula IV                                                                    wherein     H        H         13     0                                       X = H, Y=                                                                     CO.sub.2 H                                                                    P = m                                                                         ______________________________________                                    

The present invention further provides a process of producing a compoundof formula IA comprising reacting a compound of the formula:- ##STR14##wherein B and B' have their previous significance, with a compound offormula R₁ SH, wherein R₁ has its previous significance, in the presenceof a free radical initiator, and then oxidising the thiol-terminatedtelomer so obtained.

Compounds of formula IA may be conveniently prepared by reacting at atemperature of from about 24° C to 80° C in an inert solvent,appropriate quantities of a compound of the formula ##STR15## wherein Bor B' has its previous significance with a compound R₁ SH where R₁ hasits previous significance, in the presence of a free radical initiator.The inert solvent used may be any solvent or solvent system which willdissolve the reactants without reacting them per se in any substantialamount with the reactants or with the composition of the invention. Forexample ethylene glycol or dimethyl formamide may be used but water isparticularly preferred. The thiol terminated telomers are then reactedwith conventional oxidising agents for conversion either to thecorresponding sulphoxide or sulphone depending upon the degree ofseverity of the oxidising conditions and may be isolated by evaporatingthe aqueous solution to dryness, dissolving the telomer in methanol oracetone and precipitating with diethyl ether. Oxidising agents mostcommonly employed for converting sulphides into sulphones areconcentrated or fuming nitric acid, potassium permanganate, hypochlorousacid or sodium hypochlorite, chromic acid and hydrogen peroxide(inexcess) in acetic acid.

Oxidation with dilute nitric acid and with theoretical quantities ofaqueous hydrogen peroxides are used to prepare the sulphoxides. Since itis preferable to work under aqueous conditions the initiator of choiceis generally a persulphate salt but other initiators especially acylperoxides and hydrogen peroxide, which provide free radicals under thereaction conditions, could also be employed.

Other monomer derivatives may be used to obtain the same compounds offormula IA for example, acrylonitrile or methacrylonitrile, methylacrylate or methyl methacrylate. The monomers are telomerisedessentially as described above and then hydrolysed using conventionalmethods to give the completely acidic material. These alternative routesmay be preferred for economic reasons.

The inhibitor composition used according to the method of the inventionmay be incorporated into the aqueous system to be treated in conjunctionwith other compounds known to be useful in water treatment.

Dispersing and/or other threshold agents and/or scale control agents maybe used, such as for example, polymerised acrylic acid and its salts,polymerised methacrylic acid and its salts, polyacrylamide andco-polymers thereof from acrylic and methacrylic acids, lignin sulphonicacid and its salts, tannin, naphthalene sulphonic acid/formaldehydecondensation products, starch and its derivatives, alkylaminobismethylene phosphonic acids, 1-hydroxyalkyl-1,1-disphosphonic acidsand nitrilotrimethyl phosphonic acid and cellulose. Specific thresholdagents such as for example, hydrolysed polymaleic anhydride and itssalts, alkyl phosphonic acids, 1-aminoalkyl, 1,1-diphosphonic acids andtheir salts and alkali metal phosphates, may also be used.

The inhibitor composition of the present invention may also be used incombination with precipitating agents such as alkali metalorthophosphates, carbonates and hydroxides, oxygen scavengers such asalkali metal sulphites and hydrazine, and sequestering agents such asnitrilotriacetic acid and their salts and ethylene diamine tetraaceticacid and its salts. They may also be used in conjunction with corrosioninhibitors such as cyclohexylamine, morpholine, distearylamine/ethyleneoxide condensation products, stearylamine, and also in conjunction withantifoaming agents such as distearyl sebacamide, distearyl adipamide andrelated products derived from ethylene oxide condensations, in additionto fatty alcohols such as capryl alcohols and their ethylene oxidecondensates.

The following Examples further illustrate the present invention.

EXAMPLE 1

To 900g of water there were added 300 g of acrylic acid, 60g ofmercaptoacetic acid and a solution of 18.75g of sodium persulphate in300g of water. An exothermeric reaction occurred causing the temperatureto rise from 23° C to 97° C over a period of 15 minutes. After stirringat 97° C for a further 15 minutes, the reaction mixture was cooled to30° C. To the resulting solution there were added a further 300g ofacrylic acid, 60g of mercapto acetic acid and a solution of 18.75g ofsodium persulphate in 75g of water. An exothermic reaction occurredcausing the temperature to rise from 30° C to 92° C. This addition wasrepeated a further two times so that the total acrylic acid addition was1200g. After the final addition, the reaction mixture was heated at 90°C for a period of 2 hours to ensure that complete reaction had occurred.A water white solution having an active ingredient content of 54.5% wasobtained. To 500g of the above product there were added 10 mls ofconcentrated nitric acid and 90 mls of water and the solution was heatedat 95° C for a period of 10 hours.

A sample of the polymer, isolated by evaporating to dryness, dissolvingthe telomeric residue in methanol and reprecipitating the telomer indiethyl ether then drying under vacuum at 50° C for 5 hours, showedadsorption at 9.6 microns in the infra-red region of the spectrum due tothe sulphoxide group. This adsorption was absent in the infraredspectrum of the unoxidised telomer.

EXAMPLE 2

The process of Example 1 above was repeated except that in place of the10 mls of concentrated nitric acid and 90 mls of water there were used30 mls of 100 volume hydrogen peroxide. The infra-red spectrum of theoxidised polymer again showed adsorption at 9.6 microns due to thesulphoxide group.

EXAMPLES 3

To 250g of water there were added 40g of acrylic acid, 4g of2-mercapto-ethanol and a solution of 2.5g of sodium persulphate in 50gof water. An exothermic reaction occurred causing the temperature torise from 15° C to 41° C over a period of 20 minutes. The reactionmixture was heated to 85° C and maintained thus for a period of 2 hoursto ensure that complete reaction had occurred. A water white solutionhaving an active ingredient content of 13.8% was obtained. To 200g ofthe above product there were added 28 mls of 100 volume hydrogenperoxide and the solution heated to 90° C over a period of 1 hour, andmaintained thus for a further 1 hour.

A sample of the polymer isolated as in Example 1 showed adsorption of9.6 microns in the infra-red region of the spectrum due to sulphoxidegroup and had a molecular weight of 1,350 as determined by osmometry inmethyl ethyl ketone as the solvent.

EXAMPLE 4

The process of Example 3 was repeated except that in place of the 4g of2:mercapto ethanol there were used 8g of di-mercaptosuccinic acid. Awater white solution of active ingredient content 16.2% was obtained.After oxidation as in Example 3 a sample of polymer isolated by theprocedure given in Example 1 showed adsorption at 9.6 microns in theinfra-red region of the spectrum due to the sulphoxide group, and had amolecular weight of 1300 determined by osmometry in methyl ethyl ketoneas the solvent.

EXAMPLE 5

The process of Example 3 was repeated except that in place of the 4g of2-mercapto ethanol there were used 8g of 1-thio glycerol.

The polymer showed adsorption at 9.5 microns in the infra-red region ofthe spectrum due to the sulphoxide group and had a molecular weight of960 determined by osmometry in methyl ethyl ketone as the solvent.

EXAMPLE 6

The process of Example 3 was repeated except that in place of the 4g of2-mercapto ethanol there were used 8g of 2-mercapto propionic acid.

The polymer showed adsorption at 9.5 microns in the infra-red region ofthe spectrum due to the sulphoxide group and had a molcular weight of1050 determined by osmometry in methyl ethyl ketone as the solvent.

EXAMPLE 7

The procedure of Example 1 was repeated excepting that oxidation wascarried out by the following method. 300g of the polymer solution wereevaporated to dryness. The telomeric residue was dissolved in 150g ofglacial acetic acid and 56.3ml of 100 volume hydrogen peroxide added.The resulting solution was heated to 90° C over a period of 1 hour andmaintained thus for a further 2 hours. The polymer was isolated byevaporating to dryness, dissolving in methanol and reprecipitating indiethyl ether. After drying under vacuum at 50° C for 5 hours thepolymer showed adsorption at 8.6 microns in the infra-red region of thespectrum due to the sulphone group and had a molecular weight of 820determined by osmometry in methyl ethyl ketone as solvent.

EXAMPLES 8 to 14 Activity as threshold agents for calcium carbonate

2 ml. of a 1,000 ppm aqueous solution of the compound under test weremixed in a beaker with 100 ml. of an aqueous solution containing 1.47g/l Ca(NO₃)₂.4H₂ O. 100 ml. of an aqueous solution containing 0.646 g/l.Na₂ CO₃ were added and the beaker placed on a magnetic stirrer/hotplate,so adjusted that the solution warmed to 95° C (203° F) over a period of7 minutes. The solution was continuously pumped through the cell of anAutoanalyser colorimeter at a rate of 4 ml./minute and its opticaldensity recorded. From the recorded chart of optical density againsttime 5 measurements were noted.

1. The initiation time, defined as the time after mixing the twosolutions at which precipitation commenced (as judged by an increase inoptical density).

2. The rate of precipitation, defined as the maximum positive slope ofthe recorder trace, disregarding any rapid short-term increase from thebase line of less than 15% of the optical density shown by a fullyprecipitated blank solution.

3,4. The percentage precipitation which had occurred 15, 30 and 45minutes after mixing the solutions, calculated by comparing the opticaldensity at the given time to the optical density of a solutioncontaining no additives at the same times.

The results obtained using the product of Examples 1 or 2 as thecompound under test are set out in Table I which also includes datarelating to a control experiment using no threshold agent.

                                      Table I                                     __________________________________________________________________________    Activity of compounds as threshold agents                                     For Calcium Carbonate                                                                    Concent-                                                                      ration of                                                                          Initiat-                                                                           Rate of                                                                            % Precipitation in                                  Threshold  additive                                                                           ion Time                                                                           Precipi-                                                 Example                                                                            Agent p.p.m.                                                                             minutes                                                                            tation                                                                             15 mins                                                                           30 mins                                                                           45 mins                                     __________________________________________________________________________         Blank 0    1    7.9  100 100 100                                              Product                                                                  8    from                                                                          Example 1                                                                           10   8    0.3  5   12  40                                               Product                                                                  9    from  10   9    0.5  4   12  24                                               Example 2                                                                10   Product                                                                       from  10   6.5  0.69 20  48  70                                               Example 3                                                                11   Product                                                                       from                                                                          Example 4                                                                           10   10   0.60 16  32  80                                          12   Product                                                                       from                                                                          Example 5                                                                           10   8    0.39 12  32  88                                          13   Product                                                                       from                                                                          Example 6                                                                           10   10   0.30 8   30  60                                          14   Product                                                                       from  10   9    0.45 16  30  78                                               Example 7                                                                __________________________________________________________________________

EXAMPLES 15 to 21

Two brine solutions containing calcium and sulphate were prepared asfollows:-

Calcium Brine

7.5g/liter NaCl

21.6g/liter CaCl₂.2H₂ O

Sulphate Brine

7.5g/liter NaCl

21.3g/liter Na₂ SO₄

50 mls of calcium brine, containing the amount of the compound undertest to give the required concentration in the final solution, weremixed with 50 mls of sulphate brine to give a solution containing 10,000mg/liter of CaSO₄. The mixed solution was stirred in a sealed 4 oz.glass bottle 70 ± 2° C for 18 hours. At the end of the test period thecalcium concentration in the test solution was determined by titrationwith EDTA and the results were expressed in mg/liter of CaSO₄.

The results obtained using the products of Examples 1-7 or 2 as thecompound under test are summarised in Table II which also includes datarelating to a control experiment.

                  Table II                                                        ______________________________________                                        Activity of compounds as threshold agents                                     for Calcium Sulphate                                                                              Concentration                                                                             Concentration                                        Threshold agent                                                                            of active   final solution                                       active ingred-                                                                             ingredient  final solution                                Example                                                                              ient.        p.p.m.      mg/l CaSO.sub.4                               ______________________________________                                        --     none         nil.        3540                                                 Product of                                                             15     Example 1    10          8931                                                 Product of                                                             16     Example 2    10          9585                                          17     Product of                                                                    Example 3    10          8536                                          18     Product of                                                                    Example 4    10          8965                                          19     Product of                                                                    Example 5    10          8873                                          20     Product of                                                                    Example 6    10          9248                                          21     Product of                                                                    Example 7    10          9140                                          ______________________________________                                    

We claim:
 1. A method of inhibiting scale formation by salts of calcium,magnesium, barium and strontium from aqueous solutions which comprisesadding to the aqueous solution an amount within the range of from 0.2part to 500 parts per million, based on the water to be treated, of aproduct comprising a telomer of formula I ##STR16## or a salt thereof,wherein X is COOH when Y is H, or Y is COOH when X is H; B and B' areeach hydrogen, or B is CH₃ when B' is H, or B' is CH₃ when B is H; m isan integer from 2 to 100; n is 0 or 1; and R is alkyl having from 1 to22 carbon atoms substituted by one or more carboxyl groups.
 2. A methodas claimed in claim 1 wherein R is an alkyl residue having from 1 to 6carbon atoms substituted with one to three carboxyl groups.
 3. A methodas claimed in claim 1 wherein n is 0 and m is 2 to
 20. 4. A method asclaimed in claim 3 wherein m is 5 to
 20. 5. A method as claimed in claim1 wherein the amount used of the compound of formula I is within therange of from 0.2 part to 10 parts per million, based on the water to betreated.
 6. A method as claimed in claim 1 wherein a water-soluble saltof a compound of formula I is used.
 7. A method of inhibiting scaleformation by salts of calcium, magnesium, barium and strontium fromaqueous solution which comprisesadding to the aqueous solution an amountwithin the range of from 0.2 to 500 parts per million, based on thewater to be treated, of a product comprising a telomer of formula I##STR17## or a salt thereof, wherein X is COOH when Y is H, or Y is COOHwhen X is H; B and B' are each hydrogen, or B is CH₃ when B' is H, or B'is CH₃ when B is H, m is an integer from 2 to 100; n is 0 or 1; and R isa carboxymethyl, carboxyethyl, 1,2-dicarboxyethyl, carboxypropyl,carboxybutyl, 1-mercapto-1, 2-dicarboxyethyl or a group of formula##STR18## and p is a integer from 2 to 100 and may be the same as m ordifferent.
 8. A method as claimed in claim 7 wherein n is 0 and m is 2to
 20. 9. A method as claimed in claim 8 wherein m is 5 to
 20. 10. Amethod as claimed in claim 7 wherein the amount used to the compound offormula I is within the range of from 0.2 part to 10 parts per million,based on the water to be treated.
 11. A method as claimed in claim 7wherein a watersoluble salt of a compound of formula I is used.
 12. Amethod as claimed in claim 7 wherein R is carboxylmethyl, carboxyethylor a group of the formula ##STR19## wherein X is COOH when Y is H, or Yis COOH when X is H; B and B' are each hydrogen, or B is CH₃ when B' isH, or B' is CH₃ when B is H, m is an integer from 2 to 100; n is 0 or 1;and p is an integer from 2 to 100 and may be the same as m or different.